Correct Answer - Option 2 : 900

LCM of 10, 12, 15 and 18 is 180.

The factors of 10 are 2 × 5

The factors of 12 are 2 × 2 × 3

The factors of 15 are 3 × 5

The factors of 18 are 2 × 3 × 3

LCM of 10, 12, 15 and 18 is 2 × 2 × 3 × 3 × 5

= 180

So, the least number required to make 180 a perfect square is 5 as in the factors of 180, 5 is the only unpaired number.

∴ The least perfect square number which is exactly divisible by 10, 12, 15 and 18 = 180 × 5

= 900

Hence, ‘900’ is the correct answer.